138 ynides of Science. [Jan., 



this colouration to the effect of sulphur, which should be so gene- 

 rally spread about in the shape of some sulphate as to produce this 

 colouration. The author, though abstaining from stating any 

 precise cause at all inclines to the belief that the cooling effect : : 

 the cold body held in the flame has something to do with this phe- 

 nomenon. Perfectly pure hydrogen, burning from a platinum 

 burner, as well as from iron or glass burners, exhibited the phe- 

 nomenon, when cold bodies, just after haying been cleaned by 

 scraping or filing, were held in that flame. 



According to M. Bailie the moon's surface emits as much heat 

 as a cube filled with water, covered with lamp-black, ha Yin ^ 

 surface of 6 * 5 square centims., and placed at a distance of 35 metres 

 from the thermo-electric measuring apparatus employed by the 

 author for his experime^:^ 



In a paper " On the Eeflexion of Heat on the Surface of Fluor 

 Spar and other Substances. ' by 1L Magnus, we learn that the 

 following substances reflect at an angle of 45' the undermentioned 

 quantities of heat : — silver, between S3 and 90 percent.] elass, 

 between 6 and 14 percent. ; rock-salt, between 5 and 12 per cent. ; 

 fluor spar, rrween 6 and 10 per cent. The same author finds that 

 different bodies heated to 150' emit different kin;;- : beat, some 

 substances only emit one kind of heat, others, again, Tarious kinds. 

 Pure rock-salt is mono-thermic, sylvine (chloride of potassium) 

 behaves in a similar manner. 



jI. Delaurier proposes for concentrating and utilizing the sun's 

 rays, a truncated cone, open at both ends and lined inside with 

 polished silver, the sun's rays being admitted by the largest opening. 

 Since the angle of reflexion is equal to the angle of incidence, all 

 direct or reflected rays will be united at the narrower end of the 

 cone. It is clear that the greater the ler.r:L of the cone, the 

 greater will be the concentration of heat. The author enters into 

 a discussion on the advantage of this contrivance over the use of 

 lenses and mirrors, and he very enthusiastically surmises that the 

 heat of the sun's rays may be so concentrated as to serve for various 

 purposes instead of the combustion of fuel, especially in countries 

 where, as in Algeria, the heat and splendour of the sun are more 

 permanently felt than it is in our climate, 



Electpjcttx. — Our limited space prevents us from doing more 

 than allude to one or two novelties in this science. Dr. Eunspaden 

 has published a monograph on a subject first observed by Professor 

 TVohler, that when water acidified with sulphuric acid is decomposed 

 by a galvanic current, and silver is used as electrodes, peroxide of 

 silver is deposited on the anode, and metallic silver on the cathode. 

 The two main questions answered by the author by a series of 



